1. Field of the Invention
The present invention relates to a disk reproducing apparatus which reads out information from a disk on which information is recorded in digital format and performs a reproduction processing.
2 Description of the Prior Art
For example, a portable compact disk (CD) player is subject to external shock and shake. In such a case, an optical pickup is largely shifted from a tracing position on the disk, so that the signals are not correctly reproduced. To solve this problem due to shaking, the following method has been proposed:
A digital signal is pre-read from the disk at a speed higher than the reproduction speed to store the digital signal in a memory, and in order to re-read a digital signal read out erroneously, the reading position of the optical pickup is returned to the position on the signal track corresponding to the erroneously read out digital signal, so that the digital signal can be re-read and processed before a data corresponding to the digital signal is read out from the memory. Thereby, the re-reading of the erroneously data can be performed without being delayed from the actual reproduction speed.
According to this method, in FIG. 3, when the pickup jumps from a position B to a position C due to an external shake during reproduction, the pickup is returned to a position A located on the same track as the position B to perform the reproduction over again. Then, the data read out in the re-tracing is compared with a correct data on a track between the positions A and B stored in the memory. When they coincide with each other, the data read out in the re-tracing are stored in the memory from the data on the position B. That is, the data on a track including the position B and the succeeding positions are stored.
In the conventional method described above, however, if the player shakes during the comparison of the data, the data do not coincide with each other and the pickup passes the position B. Since no data on the track succeeding the position B are stored in the memory, the comparison cannot be made after the pickup passes the position B, so that the original object of preventing discontinuity in the sound cannot be achieved.
Moreover, when the data do not coincide with each other for any length of time in the comparison, the consumption of the data stored in the memory advances, and when there is no more data in the memory, the reproduction data obtained by the pickup are forcibly written in the memory to continue the data, so that a quite different data (in an example of FIG. 3, the last data in the memory is a data on a position just in front of the position B, whereas the data reproduced through the optical pickup when the data do not coincide with each other thereby to empty the memory is a data on a position far behind the position B; this data is considerably different from the data on the positions before the position B) follows the last data. As a result, a discontinuity of data is recognized in the reproduced sound.